Picture frames of the type designed to display small pictures and photographs usually include a frame member or bezel which defines a window, a sheet of transparent material filling the window and a back panel for holding the picture or photograph flat against the transparent sheet so that the picture is displayed in the window. Usually the back panel is removable to facilitate the placement and replacement of the picture in the picture frame.
The back panel may be mounted to the frame member in a variety of ways depending upon the type of frame and its cost. Some frames, particularly rectangular rolled metal ones, are provided with side and top flanges and a slot at the bottom edge of the frame member which define a keyway or slide at the back of the frame. After placing the picture in the frame window, the back panel is secured to the frame by sliding it into the keyway through the bottom slot. This type of frame construction is disadvantaged in that it can only be used on frames which are more or less rectangular. Also, the slot at the bottom of the frame member prevents the frame from having a finished edge all around its perimeter. Still further, the extra metal required to form the keyway adds to the cost of the frame.
Another conventional picture frame has a back panel which is adhered to the back of the frame member. The back panel has an opening located behind the frame window for receiving the picture and which may be closed by a drop-in cover which is retained in place by turn buttons. A major drawback of this type of frame is cost in that the finishing of the cover and the installation of the turn buttons involve time consuming manual operations.
Other types of picture frames have a back panel composed of two sections one of which is adhered to the back of the frame. The two sections are hinged together by a horizontal or vertical hinge so that the other section, located behind the frame window, can be flipped up or swung open like a book to facilitate inserting a picture into the frame. These hinged back panels are also limited to frames which are more or less rectangular.
There are also picture frames whose frame member has peripheral rearwardly extending flanges which surround the back panel, the back panel being retained in place by small pins or brads inserted into the edges of the back panel through tiny holes in those flanges. Although this type of back panel securement can be used on frames of more or less any shape and provides a finished edge all around the frame, the provision of holes for the pins and the installation of the pins add to the cost of the picture frame. Also the pins can become loose and lost if they are removed and replaced a number of times to change the picture displayed in the picture frame.